Modifications: I am knitting this cardigan seamless from the hood top down and in the round following julieknits modifications. Knitting so I do not have to seam anything :-) and I have added the reversibel cable to the bottom of the cardigan and the sleeve seams.
I finished it today Septenber 9th and I am very happy how it came out and fits! It weighs exactly 258g.

Gauge: Lovely fabric, springy and soft after washing. Knitting directly with oiled yarn.
3.00mm needles: 26st.x36rows unblocked
26st.x38rows blocked

Hood:

• Beginning with top of the hood : CO 136 st=24st for cable/88 st. for hood body/ 24st. for cable as follows: 2x68 stitches with 2mm circular needles (to have a nice tight fabric) using the Figure-8 cast-on or the Judy’s magic cast-on.
• Worked the first row on 2mm needles on the wrong side with the set-up-round of the right cable chart and row 6 of the left cable chart. Continued working with two circulars until I could put all 136st. on 1 cable needle.
• switched to 2.5mm needles the next round
• switched to 3 mm needles the next round and went on knitting with them.

Reversible Cables:
If you do knit top down as I do beware of how the cable chart is knitted!
Looking at the hood from the wrong side in front of you with the hood opening towards you, knit cables as follows (please read WS always left to right then RS right to left then next WS left to right and so on….:
Blue marker=Right cable
Pink marker=Left cable
Beginning of cable:
Set-on row on WS: Blue marker side, knit reading from L2R Row 0 and knit to Pink marker reading chart L2R knit row 6
then:
1.RS Read row 7 R2L & knit to row 1 reading R2L
2.WS Read row 2 L2R & knit to row 8 reading L2R
3.RS Read row 1 R2L & knit to row 3 reading R2L
4.WS Read row 4 L2R & knit to row 2 reading L2R
5.RS Read row 3 R2L & knit to row 5 reading R2L
6.WS Read row 6 L2R & knit to row 4 reading L2R
7.RS Read row 5 R2L & knit to row 7 reading R2L
8.WS Read row 8 L2R & knit to row 6 reading L2R

Once 1 cable repeat has been knitted it is easier to knit on on both sides of the cable.
I used a post-it to note which row I was knitting to be able to pick up the charts correctly when knitting on. After a few rows I had memorized the cable pattern and now could just knit on.

Neat cable finishing:I added 1 purl stitch after the cable to wards the stockinett part of the hood on each side: 24 cable st/1p/ 86st.st./1p/24 cable st. And so as to have a neat cable edge I knit the last stitch on WS and slipped it purlwise on RS.

I knit the hood like this until it was 15cm high and then decreased at the very back of the hood (middle line) 10 times every 2nd row 2 stitches left and right from 2 central stitches. I ended up with : 24 cable st./1p/68st.st./1p/24cable st. I knit 5 more rows before dividing the knitting for raglan sleeves increases.

Raglan sleeves:
Increases done left and right of 3 central stitches in between to make a nice raglan ridge: I divided my stitches as follows for the raglan increases:

• right front 24 cables st./1p/10st./pm/3 centre stitches/pm/right sleeve 1 st./pm/3 centre st./pm/back 36st/pm/3 centre st./left sleeve 1st/pm/10st./1p/24 left cable st.
• Raglan increases every second row 25 times. At the end of the raglan increases I had:

Right front: 24 cable st./1p/35 st./3 st raglan ridge

Right sleeve: 51 st.
picked up 7 st.underarm +6 st. raglan ridge= 64 st allin all. Knit top down in the round with following decreases:

• 3x every 5th row.
• 6x every 7th row. Sleeve measures 15cm. Knit cable edg of 5cm= sleeve is 20cm long.

Back:3 st raglan ridge/78st./3 st raglan ridge

Left sleeve:51st.
picked up 7 st.underarm +6 st. raglan ridge= 64 st allin all. Knit top down in the round with following decreases:

• 3x every 5th row
• 6x every 7th row. Sleeve measures 15cm. Knit cable edg of 5cm= sleeve is 20cm long.

Left Front:3 st raglan ridge/35st./1p/24 cable stitches.
CO 3 st. underarm each side.

Lower border: I have used the Fafner pattern from Elsebeth Lavold from Viking patterns for knitting to finish the cardigan by making mittered cables and thus finish the bottom hem with the double knitted cable all around. It looks lovely but it is very slow knitting. The cabled fabric is dense but really beautiful. I can imagine to knit the Arwen cardigan for myself one day :-)!
I would attach the cable directly when knitting the lower bord another time as SaSargantana did!